Thermally stable and low trap density SiNx/AlON bi-layer structure for AlGaN/GaN MIS-HEMTs

Abstract

We investigated a thermally stable and low trap density insulator for AlGaN/GaN metal–insulator–semiconductor (MIS) high-electron-mobility transistors (HEMTs). Current–voltage and capacitance–voltage measurements were performed before and after post deposition annealing (PDA) at 700 °C. A large increase in leakage current and high interface state density were observed after the PDA in the MIS structure with AlOx. The interface state density was reduced to one-third in the MIS structure with AlON, probably due to the reduced carbon impurity density at the AlOx/GaN HEMT interfaces. Meanwhile, the MIS structure with SiNx maintained high breakdown voltages of over 200 V, even after the PDA. By employing SiNx/AlON layers, we demonstrated low interface state density of 2.3 × 1013 cm−2 eV−1 at Ec − 0.31 eV and suppressed leakage current at −200 V. We believe that the thermally-stable bi-layer structure is a promising technology for diamond deposition to improve heat dissipation.